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Some further work on the N1 chassis this morning resulted in the roughing out of some chassis weights.

I've left 0.5mm clearances all round so that nothing can short out and to generously allow for modest intolerance's in the internal dimensions of the prints. I'm toying with the ideal of 3D printing the weights and then casting them in white metal. The calculated volume of the weights is 3.22 cubic centimeters which would make them 33.35g in white metal (27.05g in brass). Having weighed up the loco body, wheels and motor, this would bring the theoretical weight of the N1 to between 44g and 50g, with most of the weight over the drivers; by comparison, the loco end of a Dapol A3 (minus bogie and cartazzi truck) weighs in at a little over 55g . Given that the rear radial truck will be a swinging bogie, I may revisit the bunker weight in the future as it may prove to be more of a hindrance than a help.

I wondered whether you'd ever got Shapeways to print one of your designs in brass?

Hi Mike,

I can't say that I have. That's partly because of the cost and partly because the brass castings I've seen haven't been as good as I would like for the money. Having tested some RTR locos that are in the predicted weight range of the N1, I think that this will be sufficient for the tasks that will be required of it.

A start has been made in converting the chassis 3D CAD into a 2D etching artwork.

Not everything has been drawn yet and the final placement of components is yet to be decided but it is slowly coming together. The main chassis is actually two halves and not one piece as it appears here. However, the bogie will be folded up from a single piece, to help keep it aligned, and gapped for electrical isolation once the PCB spacer has been soldered in place.

The extra set of coupling rods are in case the 0.5mm lamination proves to be to thick for the Farish crankpins (it's boarder line). The second set have a half thickness back lamination which will bring the overall thickness of the rods to 0.375mm.

Annoyingly, after posting the last screen grab on here last night I noticed some misalignments between the upper and lower layers of the artwork. Something had been pulled out of position which had affected the whole of the chassis section. I had to redrawn this this morning and, lesson learnt (again!), have made a copy of the file as a backup if this happens again.

Well at the moment I'm still slowly designing stuff to etch and saving to get it made. In the meantime, I've been looking at what I can do with some bits and pieces that have been sitting around for awhile now. Therefore, I decided to turn my attention back to the J6s I was building a few years back.

The problem for me with my original efforts was that the J39 donor loco chassis was too long in both the loco and tender and spoiled the overall look of the J6 for me. I've been contemplating a solution to this problem for some time but lacked the courage to go for it.

First of all, the donor chassis placed over some scaled down drawings for Isinglass Models.

As can be seen, the front coupled wheelbase of the loco is too long (1.545mm) and the LNER tender is huge compared to the GNR one; some surgery was going to be required.

I started with the loco chassis and disassembled the whole thing. I then used epoxy glue to permanently bond the two chassis halfs together (being careful not to get glue into the recesses for the wheel bearings) and reassembled the basic block. Once everything had set, I made a 'Z' cut between the front and middle wheels, carefully cutting around the retaining screw, and filed around 1.5mm from the pieces.

I found a set of B1 coupling rods and fitted these to the J39 driving wheels and test fitted everything together. Once I was happy that the chassis parts were the right length, I elongated the front screw hole in the keeper plate and screwed everything together before carefully introducing epoxy to join the two chassis halves together. I test ran the chassis along a piece of track to ensure that there was no binding and left it overnight to harden.

The next morning, I drilled two 1mm holes into the block and pinned everything together with a couple of 1.2mm self tapping screws. Once I was happy with that the two sides of the chassis were picking up off of all wheels, I cut the heads off the screws and filed them flush with the top of the chassis. Below is a comparison photo of the altered chassis with an unaltered one.

I also had a play with the tender to see if I could somehow make it fit into a GNR tender body. By losing the DCC stuff and some modest trimming, I managed to get it to fit.

However, all but one of the J6's had tenders with an equal wheelbase and, having gone to all the effort with the loco chassis, I decided to see if I could do anything with the tender drive. Some time ago, a very talented friend of mine built me a tender drive which was powered on the rear two axles only. This works surprisingly well (and hauls twelve Gresleys on the level), so I thought I'd have a go at replicating this. I stripped the idler gears from between the front and middle axle holes and cut the chassis, shortened it and epoxied it back together. When everything has hardened in the morning, I'll fit another screw to pin the two halves together. Below is where things stand as of tonight.

Very fine work, Steve. You and the other loco builders on the forum just seem to have the necessary bits to hand.......

In my case literally years of accumulation, and speculation of grabbing parts and scrappers even if I have no current use for them.

Some have infinite usefulness - Farish 3MTs and old Farish black 5s being two of those - I almost always have a few knocking about for tasks (e.g. your standard 4MT!).

Cheers,Alan

Logged

Quote from: Roy L S

If Dr Al is online he may be able to provide a more comprehensive answer.

We have also arranged things so that almost no one understands science and technology. This is a prescription for disaster. We might get away with it for a while, but sooner or later this combustible mixture of ignorance and power is going to blow up in our faces.  Dr. Carl Sagan

Very fine work, Steve. You and the other loco builders on the forum just seem to have the necessary bits to hand.......

Thanks Mick,

My methods are much the same as Alan's, grabbing parts and scrappers as they become available. More recently, my membership to the 2mm Association has opened up some interesting possibilities, mainly swapping bodies for wheels (and occasionally chassis) with other members who build their own 2mm chassis units.

In the case of the coupling rods, these were obtained via the last source. I have enough of these to build the three J6s that have been on hold for a few years (one will be going to a new home). If I hadn't have had these, I would have probably made up a simple jig and shortened the front end of the J39 rods and soldered them back together to get the correct wheelbase. The chassis themselves are back from when Farish sold NQPs at competitive prices.

Parts accumulate reasonably quickly, although some projects can wait for years while you wait for suitable donor parts to turn up.

I've test printed the J6 body to ensure everything fits as it should. A couple of minor changes to be made, but overall it's not looking too bad.

The tender was one of my initial prints for the C1 and technically is the wrong type for most of the J6 class. However, the overall proportions are the same and it was a quick and easy way to see if I could make the shortened Farish tender drive fit. I'll design up the more common tender paired with the class in due course.

That is looking really good Steve. I know we have discussed the relative merits of a stretch of loco and tender bodies to fit the unaltered J39 chassis, but I have to concede that the chassis modifications you have made were really worth it.

The loco, even in current far from finished form looks "right" as it is now and I am really looking forward to seeing this one progress.

I've started designing yet another locomotive (I really should finish a few!).

The loco will make use of some 6'6" ABS/Beaver wheels I have as they are the best compromise between diameter and practical fit; although I'll have to turn the flanges down a little. Even then, I've had to shorten the wheelbase at the back by 0.5mm to get it to fit when scaled down to N gauge. The bogie wheels will be the largest Farish type, which is underscale but only just allows clearances once the flange is taken into consideration.

I'll probably use a tender drive for this loco which will also be to the benefit to the J6s.

I've started designing yet another locomotive (I really should finish a few!).

The loco will make use of some 6'6" ABS/Beaver wheels I have as they are the best compromise between diameter and practical fit; although I'll have to turn the flanges down a little. Even then, I've had to shorten the wheelbase at the back by 0.5mm to get it to fit when scaled down to N gauge. The bogie wheels will be the largest Farish type, which is underscale but only just allows clearances once the flange is taken into consideration.

I'll probably use a tender drive for this loco which will also be to the benefit to the J6s.

Yet another loco for your Hadley Wood roster that I look forward to seeing develop very much Steve, keep up the great work!